Novak Djokovic survived his first serious test of the ATP Tour Finals as the world No.1 advanced to the final with a 6-1 3-6 6-0 victory over Japan’s Kei Nishikori on Saturday.

Djokovic had swept through the group stage at London’s O2 Arena in imperious style, but he was pushed harder by Nishikori, who became the first player to take a set off him this week, before a strong finish secured the Serb’s fourth appearance in the final of the prestigious season-ending event.

“Kei was playing great and this has been the best season of his life but he made some crucial double faults in the third set,” Djokovic said.

The 27-year-old has now won 31 successive indoor matches, including 14 at the Tour Finals, and his final opponent will be either six-time champion Roger Federer or Stan Wawrinka, who meet in an all-Swiss semi-final later on Saturday.

“Of course I will watch the other semi-final. I’ll get some popcorn and enjoy it from my bed,” Djokovic said.